The present disclosure relates generally to validation of the time dependence of the ON-state drain-source resistance (Rdson), after high voltage stress in the OFF state. Rdson is a key figure-of-merit for high-voltage Gallium Nitride (GaN) MOSFETs (GaNFETs). At high temperature, some GaNFETs may exhibit a degradation of the on-state drain-source resistance (Rdson) after being subject to high drain-source voltage (Vds) in the off state. This phenomenon, which may also be referred to as current collapse, reflects the drop in drain-source current that is a corollary to the increase in Rdson. The phenomenon is transient and temperature dependent. At high temperature, this transient Rdson evolves very quickly—for example, in less than one second—after the GaNFET is switched on. An accurate estimate of the transient Rdson is advantageous in assessing GaNFET performance and in screening of devices that exhibit current collapse. Thus, there is a need in the art for systems and methods that enable the continuous estimation of transient Rdson on a plurality of parts effectively simultaneously and at preselected temperatures in excess of ambient temperatures.